Krauss-Maffei Diesel-Hydraulic locomotives on the D&RGW 1

After a very long time on the RIP track, I've decided to haul our blog RAILROAD LOCOMOTIVES out of the weeds and place it back into service. Here's the first new run.

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Krauss-Maffei Diesel-Hydraulic locomotives on the D&RGW 1

I have been very fortunate recently to acquire some new material which describes the type ML4000C'C' diesel-hydraulic locomotives built by Krauss-Maffei of Munich, Germany and which were delivered to two U.S. railroads (Denver & Rio Grande Western, three units, and Southern Pacific, three units) in August 1961. While very much has been written and repeated about locomotive design in the United States up until the time that the arrangements were made to construct these units and the effect this had on the desire to increase unit horsepower, very little has been presented in the English language in a brief form to explain the background behind their development in Germany. Using the newly found materials, and a number of documents and magazine scans sent to me over six years ago by Steve Palmano, I'll try to fill in both some of the background information and some design details of these units.

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Development in Germany prior to 1960

The earliest developments in hydraulic transmissions for use in diesel locomotives in Germany, prior to the war, did not result in anything which we would consider full capacity road locomotives here in the United States. After the war, the nationalized West German railway system, known as the Deutsche Bundesbahn or most often simply DB decided that it would eventually have to embark on either electrification (which was highly desired) or else dieselization and developed a series of specified design parameters for locomotives which were grouped into a designation system with "V" designators. For example, in this overall plan, there was to be a switching locomotive for very low speed service known as the V60 which would be rated roughly 600 horsepower - that is to say, the diesel engine installed would have a brake horsepower rating of 600. Below, a diagram of a V60 from our copy of the 1960 Henschel Locomotive Engineer's Manual showing external view and internal details.

In this view, the diesel engine is easily made out under the larger of the two hoods, with high speed drive shaft to the hydraulic transmission. The transmission then drives the jackshaft which is connected to the driving wheels by side rods just like steam locomotives or some electric locomotives.

Moving more toward our story, now, the DB made the move in 1951 to apply this kind of technology to a true road locomotive. Clearly, side rods were not permissible and so trucks would have to be used; also, a steam generator to heat passenger cars was desirable to give the locomotive dual service capability. The DB had also provided a specification for a new range of diesel engines to be used in diesel-hydraulic locomotives that spurred competition between engine makers because it clearly implied that large contracts for production engines might be in the offing. The specification did however push the envelope of existing engine technology because of the requirements for very high power to weight ratio and the statement of a required top running speed of 1500 RPM.

The result in 1951-1952 was the construction of ten V80 class prototype locomotives. Three different makes of diesel engine were used experimentally - these being Daimler-Benz's Mb820Ab, the M-A-N L12V 17.5/22B, and the Maybach MD650. All were high speed V-12 four stroke diesel engines with what in European circles is referred to as pressure charging by exhaust-driven turbosupercharger. We simply use the term "turbocharged." Although the engines were of similar size envelope, there were many construction detail differences and the fact was that the M-A-N engine was fairly bad in service while the other two were good. Below, a V80 locomotive photo from the Henschel manual.

In these locomotives, two different makes of hydraulic transmission were used; the Voith Turbo and the Maybach Mekhydro. The Voith was a complicated unit that used three different torque convertors which were emptied and filled automatically, giving a starting high-torque range and two running speed ranges. The Maybach unit used one torque convertor and four power shifted gears, like a large automobile transmission. On both, shifting was totally automatic; inputs to shift control were throttle position and track speed.

A number of detail problems were made quickly apparent by these units, most notably the tendency of the long intermediate drive shafts from the transmission (centrally mounted) to the two truck assemblies to twist under heavy load. In later units of this size and power range, the transmission was much lower and very short shafts used to the trucks in order to avoid this torque twisting.

The "type" program now evolved into two important types for road service - a V100 of about 1000 HP based on the V80, with improvements, and a large road locomotive of twice the power to be called V200. The V200 was the first large diesel-hydraulic road locomotive type in the world; these were built beginning in 1953 with several prototypes. Below, the V200.

The well publicized tour of one of the original units of this type over a large portion of Europe, sponsored by its builder, Krauss-Maffei, spurred the order for three locomotives of modified design for Yugoslavia. These units were slightly longer, had six axles instead of four, and had two 1100 HP engines. These were classed by Krauss-Maffei as its ML2200 type.

One further six-axle unit of this type was built in 1957 for testing in Germany. As the decade was moving to an end, there was a massive rush of locomotive development in Germany. At once, much higher powered engines and hydraulic transmissions capable of taking their output began to be developed, in part in response to the specification for a single-engine locomotive between the V100 and V200 in output. This would become the V160, first actually built in 1960. Below, a view of one of the first prototype V160 locomotives.


For this range of locomotive, both Maybach and Daimler-Benz had developed 16 cylinder high speed engines of 1600-2000 HP output range; Voith and Maybach were hard at work to produce transmissions which could handle the output.

The most important step in the development between the ML2200 and the ML4000 was the conversion of the single German ML2200 into the prototype ML3000 in 1959. This involved replacing the original MD650 engines with MD655 engines; these Maybach 12-cylinder engines were very much the same except that "charge air cooling" or intercooling was employed, with a higher boost pressure. The new engines were rated 1500 brake horsepower; new Maybach Mekhydro transmissions of type K184 were installed that could handle the increased output. The locomotive immediately proved very powerful and capable.

This locomotive (when completed in new form in the first quarter of 1958) was rated a total of 3000 brake horsepower, had a weight in working order, fully loaded of almost 114 short tons (a very high power to weight ratio,) a starting tractive effort at 30% adhesion of 65,800 lbs when 2/3 loaded, a continuous drawbar rating of 59,500 lbs at 12.3 MPH and a top speed of 87 MPH. This was probably the first diesel-hydraulic road locomotive that approached characteristics that could get the attention of U.S. railroads in a serious way. Krauss-Maffei continued its efforts to construct locomotives for export in addition to continuing to build "V" classification locomotives for the DB, and the stage was set for immediate development of the ML4000 by simple extrapolation.

NEXT TIME: THE ML4000C'C' IN DETAIL